How to customize bibliography style and citations?

Question

I have a problem customizing my bibliography format, I need the citation to be in author/year format which is now displaying correctly, however I need to put square brackets around each citation and a comma in between the author/year.

My citation now is showing as:

Author 1991

Instead I need it to be as follows:

[Author, 1991]

Also in the bibliography page where it shows all the references in the last page, currently it is displaying as follows:

Author (1991)."XX publication". XX publisher, pp. X–X

But I need it to show in two lines adding the citation abbreviation in the first line then the reference in the second, also I need to add the year in the end after the publisher and with no parenthesis. The references must be ordered alphabetically by author name which is showing correctly now. The required format is as follows:

[Author, 1991]

Author."XX publication". XX publisher, 1991, pp. X–X

Here is what I am using currently:

\usepackage[
backend=bibtex,
style=authoryear,
citestyle=authoryear
]{biblatex}
\addbibresource{example.bib}

and for the bibliography page:

\setlength\bibitemsep{2\itemsep}
\printbibliography[heading=bibintoc, title=References, resetnumbers=true]

here is a sample from my "example.bib" file:

@article{11,
    author = {Author},
    title = {XXX},
    journal = {IEEE},
    year = {1991}
}

And here is an example of my citation:

\cite{11}

Answer 1

I think that the biblatex-ext styles can do everything that you need. As I mentioned in the comment, you should remove backend=bibtex from your loading options for biblatex and compile with biber instead.

To achieve the [Author, Year] format in citations you have two options. You can use the \autocite command, or you can use the \parencite command. Using \autocite has an advantage if you may need to use very different citation styles across different versions of a document, since it will adapt to other styles automatically. If you only use an author-year style then using \parencite / \textcite (which yields Author (Year) format) is also fine.

\documentclass{article}
\usepackage[citestyle=ext-authoryear,
            bibstyle=ext-authortitle,
            introcite=plain,articlein=false,sorting=nyt]{biblatex}
\DeclareOuterCiteDelims{parencite}{\bibopenbracket}{\bibclosebracket}
\DeclareDelimFormat{nameyeardelim}{\addcomma\space} 
\DeclareFieldFormat{bbx@introcite}{\mkbibbold{\mkbibbrackets{#1}}}
\DeclareFieldFormat{issuedate}{#1}
\renewcommand*{\introcitepunct}{\par}
\renewcommand*{\volnumdatedelim}{\addcomma\addspace}
\setlength{\bibhang}{0pt}
  

\addbibresource{biblatex-examples.bib}
\begin{document}
\autocite{bertram} % \parencite also works here
\printbibliography
\end{document}